1. Field of the Invention
This invention is concerned with placing a liquid, a past, powder or a solid sample on a screen in order that a spectrum can be determined in a spectrometer, with the screen being fixed to a holder which will permit the screen being placed in the energy beam of the spectrometer.
2. Description of the Prior Art
The art of placing samples in spectrometers is a very old one and was well developed prior to 1940. Although developments in placing samples is spectrometers in order that their spectra may be determined is very well established in infrared spectrometers, and in particular in Fourier Transform Infrared (FTIR) Spectrometers, parallel developments have also taken place in UV spectrometers, visible light spectrometers, near infrared spectrometers, far infrared spectrometers, Raman spectrometers and fluorescence spectrometers to achieve the same ends. The attention will largely be concentrated on the FTIR spectrometer.
In order to determine qualitative spectra of liquids, solids and pastes, several methods have been developed. FIG. 1 shows a device known as a demountable cell. Two suitable windows of IR transmitting material, such as sodium chloride 1 are held in place by a retaining ring 2 which is held in position three bolts and nuts on a mounting plate 4 which fits into the cell slide of all commercial FFIR spectrometers. The cell slide insures that the sample held between the windows 1 will be in the energy beam of the spectrometer. The remountable cell, FIG. 1 is loaded by placing one or two drops of liquid between the windows 1 and placing the windows 1 on the plate 4 attaching the retainer ring 2 to upright bolts 3 and placing a nut on each bolt 3 and tightening down to the desired level. The cell is simple to assemble and disassemble, but the sodium chloride windows are expensive, subject to attack by moisture and many solvents, and is fragile. The use of the demountable cell applies to liquids or pastes but not to solids.
FIG. 2 depicts a card 5 containing a porous polyethylene or porous polytetrafluoroethylene window 6 upon which a sample of liquid or solution of a solid, or a paste can be placed. The card, FIG. 2, is then placed in the cell slide of an FTIR spectrometer and a spectrum determined. The problem with this device is that the spectrum of the porous paper is also determined in addition to that of the sample applied to the card window. This complicates the interpretation of the IR spectrum and renders information in four critical areas of the spectrum uncertain in the case of the polyethylene window, and several valuable areas am also useless when the polytetrafluoroethylene paper is used.
Thus, no simple means is presently available in commerce to obtain an FTIR spectrum of a liquid, paste or solid sample untrammeled by an additional spectrum.